Diabetes is a leading cause of cardiovascular disease, end-stage renal disease, blindness and debilitating neuropathies. Hyperglycemia is the root cause of these maladies, but the mechanisms of glucose toxicity are unclear. Hyperglycemia and oxidative stress dramatically increase the enzymatic modification of proteins by 0-linked N-acetylgiucosamine (0-GlcNAc), an endpoint of the hexosamine biosynthetic pathway. 0-GlcNAc is a dynamic regulatory modification that is both analogous to, and is as abundant as protein phosphorylation in all multi-cellular organisms and viruses that infect them. Dynamic crosstalk between OGlcNAc and phosphorylation serves as a nutrient/stress sensor to regulate signaling, transcription and cytoskeletal assembly. Increased nutrients in the blood, including amino acids, fatty acids and glucose, all increase GlcNAcylation of cellular proteins. Mounting evidence indicates that elevated GlcNAcylation underlies both insulin-resistance and glucose toxicity. We have assembled a multi-disciplinary team comprised of basic scientists and clinical investigators who are experts in diabetic cardiomyopathy, diabetic retinopathy, diabetic neuropathy and hyperglycemia-induced beta-cell destruction, to elucidate the common fundamental mechanisms underlying glucose toxicity. It is our hypothesis that nutrient-induced hyper-GlcNAcylation is a fundamental mechanism of glucose toxicity, affecting many different cellular processes, including increasing the generation of reactive oxygen by the mitochondria via abnormal GlcNAcylation of electron transport chain components, dysregulation of protein kinase C and other kinases, altering the activity and specificity of transcription factors (eg. SP1), and via affecting functions ofpolyols. By assembling a team of clinicians and biochemists to study glucose toxicity in different model systems that are most relevant to human disease, and in patient samples, we will not only uncover common disease mechanisms, but also will learn how glucose toxicity differentially affects individual tissues. These studies will lead to novel avenues of treatment and prevention of diabetic complications. PUBLIC HEALTH RELEVANCE: Diabetes is amongst the most prevalent diseases in the Western world. The morbidity and mortality of diabetes is largely due to glucose toxicity. Yet, little is known about the molecular mechanisms as to why excessive glucose is toxic to tissues. We have assembled a team of both medical experts and biochemists to uncover the mechanisms of glucose toxicity in tissues most affected in the disease. The data obtained will allow the development of new preventions and/or treatments.